Implement non-player recipients (#131)

* Implement non-player recipients

* Add API callback specifically for players receiving mail

* Exclude sender from (mailing list) recipients

* Complement test

* Fixup typos in complemented test

* Expand aliases at toplevel if the current expansion is at toplevel

This should allow players to send mail to their own aliases

* Also test on_(player_)receive callbacks

* Fix oversight in test case

api.spec.lua

@@ -1,12 +1,56 @@
+mail.register_recipient_handler(function(_, name)
+    if name:sub(1, 6) == "alias/" then
+        return true, name:sub(7)
+    elseif name == "list/test" then
+        return true, {"alias/player1", "alias/player2"}
+    elseif name == "list/reject" then
+        return false, "It works (?)"
+    end
+end)
+
+local received_count = {}
+mail.register_on_player_receive(function(player)
+	received_count[player] = (received_count[player] or 0) + 1
+end)
+
+local sent_count = 0
+mail.register_on_receive(function()
+	sent_count = sent_count+1
+end)
+
+local function assert_inbox_count(player_name, count)
+    local entry = mail.get_storage_entry(player_name)
+    assert(entry, player_name .. " has no mail entry")
+    local actual_count = #entry.inbox
+    assert(actual_count == count, ("incorrect mail count: %d expected, got %d"):format(count, actual_count))
+    local player_received = received_count[player_name] or 0
+    assert(player_received == count, ("incorrect receive count: %d expected, got %d"):format(count, player_received))
+end
+
 mtt.register("send mail", function(callback)
-    -- send a mail
-    local success, err = mail.send({from = "player1", to = "player2", subject = "something", body = "blah"})
+    -- send a mail to a list
+    local success, err = mail.send({from = "player1", to = "list/test", subject = "something", body = "blah"})
     assert(success)
     assert(not err)
+    assert_inbox_count("player2", 1)
+    assert_inbox_count("player1", 0)
+    assert(sent_count == 1)
+
+    -- send a second mail to the list and also the sender
+    success, err = mail.send({from = "player1", to = "list/test, alias/player1", subject = "something", body = "blah"})
+    assert(success)
+    assert(not err)
+    assert_inbox_count("player2", 2)
+    assert_inbox_count("player1", 1)
+    assert(sent_count == 2)
+
+    -- send a mail to list/reject - the mail should be rejected
+    success, err = mail.send({from = "player1", to = "list/reject", subject = "something", body = "NO"})
+    assert(not success)
+    assert(type(err) == "string")
+    assert_inbox_count("player2", 2)
+    assert_inbox_count("player1", 1)
+    assert(sent_count == 2)
 
-    -- check the receivers inbox
-    local entry = mail.get_storage_entry("player2")
-    assert(entry)
-    assert(#entry.inbox > 0)
     callback()
 end)